Vacuum pump from refrigeration compressor questions

How are you going to address the lubrication of the compressor? In a refrigeration system the lubricant circulates with the refrigerant to circulate through the cyls. When used as a vacuum pump this does not happen.

Will it work? Sure - for a while. How long? Who knows - but the pump will deteriorate with use.

Actually, from what I have seen on YouTube, the compressor gets adequate lube, especially the refer types which actually have the motor submerged in oil.

Won't you be sucking a lot of moisture? That can't be good. I'd at least think about the possibility of getting vapors from the compressor back into your food.

Educate me on the value of high vacuum food preservation.

For bag sealing like seal-a-meal, the purpose of the vacuum is to EXCLUDE air by forcing the plastic into contact with solid chunks of food, like chicken breast. Once contact has been achieved, higher vacuum has no purpose. I suggest it's a detriment. The higher the vacuum, the more likely you'll hasten the exit of water from the food into any voids that exist.

I bought a bunch of rigid plastic containers with vacuum inputs at a garage sale and tried to learn how to use them.

I concluded that: If you can't force the container into contact with the food, the best you can do is to exclude air with vacuum. The seal-a-meal vacuum pump I have couldn't do much better than removing 2/3 of the air. If Oxygen is what causes food to go bad, higher vacuum removes more of it. If you use higher vacuum, you suck moisture out of the food. If that results in a puddle somewhere, that can't be good. I assume you wouldn't want to wait long enough for all the moisture to be removed by the pump. Higher vacuum probably results in more air and/or pathogens being sucked in over time thru tiny leaks.

A nitrogen purge might be better than trying to extract the oxygen directly with a vacuum pump.

Bottom line is that my rigid vacuum sealed containers are sitting quietly in the attic awaiting my next garage sale.

The motor is submerged in oil for cooling - the actual compressor is still not adequately lubricated in many cases.

Bottom line is that my rigid vacuum sealed containers are sitting quietly in the attic awaiting my next garage sale. ===================================================

I don't know how big they are, but especially if they have transparent lids they might work well as degassing chambers if you ever get into casting polymers like polyurethane ... If nothing else, suggest it on your price tag when you do the yard sale :-).

Eric - you might try Harbor Freight's air powered vaccum pump. According to memory, 4 cuft/min power required for 25 inches vacuum. $14 or thereabouts.

Hul

snipped-for-privacy@whidbey.com wrote:

The principal drawback is volumetric efficiency. Reefer compressors are usually piston-type with finite compression ratio. Vacuum pumps are usually rotary vane types with (ideally) infinite compression ratio.

Whether that matters depends entirely on the base pressure you want to achieve. For food, the base pressure will be around the vapor pressure of water. At room temperature that's about 20 torr. A piston compressor needs a compression ratio of roughly 40 to get there when exhausting to atmosphere, and its efficiency is zero in that limit.

40 seems like a rather high compression ratio, purely from a mechanical point of view. It would be surprising if a reefer compressor is that good.

hth,

bob prohaska

Mechanical vacuum pumps tend to backstream pump oil when the pressure starts getting down. You commonly use a cold trap (LN2) in applications that won't tolerate pump oil in the vac chamber. Might add a strange taste to the food!

BobH

...

If the goal is storing frozen foods while avoiding freezer burn, pulling the air out of aluminized mylar or thick polyethylene sacks, then heat-sealing, is ok; if that's properly done, foods keep ok months to years. For storing well-dried non-oily foods at room temperature for similar times, the same technique works ok. An oxygen absorber deals with trapped air and allows longer storage.

But long-term storage, eg 30 years, at room-temperature, freeze drying is about the best approach. The vacuum-freeze-dry process (see ) doesn't collapse food cells as much as heat-drying does, freeze-dried food weighs a little less than heat-dried, and it rehydrates much more nicely than heat-dried food.

See eg for some various at-home freeze-drying models, $2300 to $4100 on sale. Of course most RCMers could put together something that would work, for much less than that. But if you are going to make a freeze dryer and run it full time, several food batches per week, with different temperature and vacuum vs time profiles for different foods, and depend on the unit making food that's safe to eat, conveniently and dependably, that may run the cost up into the same ballpark.

On the "Harvest Right Freeze Dryers" facebook page, water in the vacuum-pump oil gets mentioned, as well as pump oil going where it shouldn't be. The company has a recommended oil change schedule. sells a kit with valves and filters to get water etc out of the pump oil after each batch. has a lower cost manual filter system. These companies are in the SLC UT area -- LDS recommends a three-month short-term food supply, plus a supply of long-lasting (30 year) foods as well.

Anyhow, having your own freeze-dryer makes sense if you have a bountiful garden and access to lots of produce or if you want to make and store hundreds of servings of almost anything for future consumption. Otherwise it's less expensive to order freeze dried foods from companies like Augason Farms in SLC, although Walmart at often has the same prices as AF. Eg about $31 for a 25-year-shelf-life #10 can with 24 servings of Augason chili-mac w/ freeze dried beef, $23 for 14 servings of Freeze Dried Chicken Fettuccine Alfredo with best-before date of 1 May 2042, $90-$100 for 307-serving AF 30-Day All-In-One Emergency Survival Food Supply Kit, etc.

I don't know how high a vacuum I ned. Certainly not milli torr levels. But the food will be as dry as I can make it befaore vacuum packing. The vacuum is to just remove as much oxygen as possible. I have been pressure canning in jars for years and recently started using cans instead of jars be cause of durability and light exclusion. The foods that I pressure can get eaten on a regular basis, they just cycle through the pantry. But since I do live near a pretty big fault and an earthquake is possible I think I need to have a months worth of food stored that I don't need to worry about. Hence very dry. And water stored as well for the same month. Eventually I will have the water, dry food, and conventional fully cooked and canned food enough for a month set away. Eric

Thanks for all the good info James. There are dietary issues my wife has but I'll bet most if not all will be addressed with the foods available now. So much "prepper" and "survivalist" stuff is hyped now prices on a lot of stuff is way high. The LDS does offer some stuff and there is a store not too far away from me. I don't know if the effort to freeze dry myselfwould be worth it except just to say I did it and could do it again. But that's exactly the kind of thing I like to do and I would imagine freeze drying a few months worth of food wouldn't be that big of a deal. Thanks Again, Eric

Apparently the air conditioner compressors are usually the vane type while refers use pistons. Here in the US that is. Eric

This is the wrong place for this discussion, but what the hell... A couple of years ago, I realized that I was totally unprepared, so I looked into it. I decided that I needed a stockpile of heirloom seeds and some practice farming. I downloaded a book on how to do some doctor/health stuff. I'd need at least a year worth of food to get the garden growing. I'd need a lot of stuff to barter. Bank account is useless if the bank no longer exists. The more physical stuff you have, the more you need an army to protect it.

Thought about it and decided that disasters run the gamut from highly personal, (your house explodes) to cataclysmic (nuclear war or meteor hit).

I don't live on an island, so up to a certain point, I can grab the cash under the mattress, get in my car and go where the disaster isn't. Past a certain point, I'm unlikely to survive, no matter what I do.

You can prepare for the range between those two points. I concluded that the range of disaster that lies between those points isn't very large. Preparation would require moving to the country, building a farm compound, recruiting professionals, like a doctor, farmer... That's not practical for most of us. The cost/benefit ratio is extremely high. I don't want to live out my life like that just in case, maybe, possibly there might be a survivable disaster.

The post-apocalyptic world belongs not to the one with a year's supply of dried food. It belongs to the one with gang affiliation and the most ammo.

Excuse me, I gotta go to WalMart and pick up some stuff with a lot of sugar and saturated fat...I should probably pick up some ammo... ;-)

I just wanna be prepared in case of a temporary disaster situation. My neighbors may not have what they need so I may need to help them with food and water. I don't expect a month of food is what my wife and I would need, but it may be what us and some neighbors need. I am on an island, and on a well. Earthquakes can disrupt wells. So water storage is a must. If it all really goes to hell then I'll be oughta luck. Eric

+10

Somebody is using his head, unlike the average "prepper." And the older we get (like me), the more absurd the entire paranoid enterprise looks.

BTW, make sure that the ammo you buy is US-made. You don't want to boost someone else's economy. d8-)

Yeah, I see a lot of preppers that are old dudes but their behaviour is like a teenage boy's fantasies of saving the world and getting the girl. Eric

This is a way bigger problem than you might expect. Proper vacuum pumps emit noxious oil mists too especially when pumping down stuff that's wet and won't allow a hard vacuum anyways. There are good quality clear oils that don't smell as as bad as others, but it's still gross.

Nope, the gangs will get the families who aren't armed, but by then, those with arms will take out the gangs.

On an island, you need a large desalination plant with lots of backup media, Eric. Trade water for everything else you need. After you buried your saltwater source and fenced the crap out of your compound.

- The list of Obama administration disappointments would take three rolls of toilet paper to record. --BMF

The first thing you do is NEVER TELL ANYONE YOU HAVE FOOD STORAGE. I thought you knew that.

How did you get water?

- The list of Obama administration disappointments would take three rolls of toilet paper to record. --BMF